Engineers at Harvard University have designed the first 3D-printed, autonomous robot that transitions from a rigid body to a soft one which can jump. Powered by a mix of butane and oxygen, it can jump more than 20 times its own height, yet land upright.

The team of engineers from Harvard University and the University
of California San Diego (UCSD) wanted the autonomy and speed of a
rigid robot, with the adaptability and resiliency of a soft
robot. Using a multi-material 3D printing process, the team
combined stiff plastic and squishy rubber in nine layers of
printed materials to create the jumping robot.

“This robot is a demonstration of a method to integrate the
rigid components with the body of the soft robot through a
gradient of material properties, eliminating an abrupt,
hard-to-soft transition that is often a failure point [in robotic
design],” said Robert J. Wood, Harvard’s Professor of
Engineering and Applied Sciences, and senior author of the study,
in a statement

The robot comes with a core body featuring a custom circuit
board, a high voltage power source, a battery, an air compressor,
butane fuel cells, six valves, an oxygen cartridge, and a
pressure regulator and ducts to move the gas around.

To jump, the robot inflates one or more of its pneumatic legs to
point the body in the direction it wants to move to, fills the
body with a mixture of oxygen and butane, and then ignites
itself. This expands the flexible bottom of the robot, propelling
it into the air.

The robot can jump more than 20 times and reach more than 2.5
feet (0.75 meters), or six times its own height. It also moves
half a foot (0.15 meters) laterally.

Integrating rigid and soft materials has challenged robotic
engineers for years.

“[Bringing] together soft and rigid materials will help
create a new generation of fast, agile robots that are more
robust and adaptable than their predecessors and can safety work
side by side with humans,” said Michael Tolley, an assistant
professor of mechanical engineer at UCSD, and the paper’s co-lead
author, in a statement.

Tolley said the inspiration for blending soft and hard materials
came from nature. Certain species of mussels have a foot that
starts out soft and then becomes rigid at the point where it
makes contact with rocks.

“In nature, complexity has a very low cost,” Tolley
said. “Using new manufacturing techniques like 3D printing
we’re trying to translate this to robotics.”

Researchers describe the robot’s design, manufacturing and
testing in the July issue of Science magazine.